Herein is reported the asymmetric allylic benzylation of Morita-Baylis-Hillman (MBH) carbonates with 2-methylbenzophenone (MBP) derivatives as nonstabilized photogenerated C-nucleophiles. The dual activation of both reaction partners, chiral Lewis-base activation of the electrophile and light activation of the nucleophile, enables the stereoselective installation of benzyl groups at the allylic position
The cinchona alkaloids are a privileged class of natural products and are endowed with diverse bioactivities. However, for compounds with the closely‐related oxazatricyclo[4.4.0.0]decane (“oxazatwistane”) scaffold, which are accessible from cinchonidine and quinidine by means of ring distortion and modification, biological activity has not been identified. We report the synthesis of an oxazatwistane
diastereoselectivities (>95:5) via a DABCO‐mediated [2+1] annulation. Utilization of enantiomericallypurecinchonaalkaloid derivatives enables the first asymmetric ammonium ylide mediated method to provide (3R , 4R )‐β,γ ‐disubstituted and (2R , 3R, 4R )‐α,β,γ ‐trisubstituted γ ‐butyrolactones in moderate to good yields with up to very good enantiomeric ratios (97:3). The scalability of the transformation
Asymmetric Alkylation of Anthrones, Enantioselective Total Synthesis of (−)- and (+)-Viridicatumtoxins B and Analogues Thereof: Absolute Configuration and Potent Antibacterial Agents
作者:K. C. Nicolaou、Guodu Liu、Kathryn Beabout、Megan D. McCurry、Yousif Shamoo
DOI:10.1021/jacs.6b12654
日期:2017.3.15
this naturally occurring antibiotic. While the developed asymmetricsynthesis of C10 substituted anthrones is anticipated to find wider applications in organic synthesis, its immediate application to the construction of a variety of designed enantiopureanalogues of viridicatumtoxin B led to the discovery of highly potent, yet simpler analogues of the molecule. These studies are expected to facilitate
描述了使用奎尼丁或奎宁衍生的催化剂相转移催化蒽酮与环状烯丙基溴的不对称烷基化。利用温和的碱性条件和低至 0.5 mol % 的催化剂负载量,并实现高达 > 99:1 dr 的选择性,这种不对称反应成功地应用于对映选择性地产生 (-)- 和 (+)- 绿藻毒素 B,从而允许分配这种天然抗生素的绝对构型。虽然开发的 C10 取代蒽酮的不对称合成有望在有机合成中找到更广泛的应用,但其直接应用于构建各种设计的 viridicatumtoxin B 的对映体纯类似物,导致发现了高效但更简单的分子类似物。
Tertiary Amine-Catalyzed Chemoselective and Asymmetric [3 + 2] Annulation of Morita–Baylis–Hillman Carbonates of Isatins with Propargyl Sulfones
A chemo- and enantioselective [3 + 2] annulation of Morita–Baylis–Hillmancarbonates of isatins with propargyl sulfones was catalyzed by a β-ICD O-MOM ether 1c, affording spirocyclic 2-oxindoles bearing an unusual cyclopentadiene motif in outstanding ee values (up to >99%). More electrophiles, such as N-phenylmaleimide, have been also utilized to deliver complex spirocyclic 2-oxindoles with good results